I was looking at a 757 being loaded the other day and was wondering why Boeing made this a/c stand up so high off the ground. The 737 is bulk loaded and is able to be loaded and unloaded without the use of baggage belts and as the 757 is also bulk loaded I don't understand why they had to make it stand so high off the ground.

I was looking at the engines they do not seem any bigger than those on the 733/4//5/6/7/8 so didn't seem like they required the extra height for ground clearance, after all could they not have just flattened the bottom like they did on the 733 onwards if that was an issue and made the a/c lower to the ground ?.

I then thought about the extra height being required to give the tail more ground clearence on rotation due to the extra length of the a/c, but ruled this out due to the fact that the B739 is just about the same length but is still lower to the ground.

One of the considerations by Boeing, was to design the 757 with a thought of a fuselage stretch... as a matter of fact, this made the 757-300 possible...
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Boeing had a bad experience in the late years of the production of the 707... Douglas had been able to stretch the DC8 into the 61 and 63 series, and it was impossible to Boeing to match the stretch of the Douglas fuselage, because of tail clearance for rotation being limited with the 707...
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Happy contrails...
(s) Skipper

As ever, the Skipper knows the score. Boeing would have done much better with the 707 if the gear had been taller and allowed a stretch. Shame they left it so late with the 757 - if the -300 had happened a decade ago the 757 might still be in full production now.

Leezy... Boeing determined the cost of a full gear re design, likely with new wings, engine, etc... would be to great to justify the program. The lack of stretch capability on the 707 accelerated Boeing's efforts to build a larger airplane, leading to the 747. Of course, something bigger would of probably come along anyway, but this made the matter of building a big plane more urgent.